Final answer:
The correct term for data added to packets for routing and reassembling the original message is 'Header'.
Step-by-step explanation:
The term for data added to packets to help route them through the network and reassemble the original message is c) Header. The header contains various types of information necessary for data transmission, including source and destination IP addresses, segment information, and other network protocols to ensure that data packets reach the correct destination and can be correctly reassembled into their original form.